What is the molar mass of 65.18 g of gas exerting a pressure of 2.25 atm on the walls of a 4.81 l container at 350 k?

Molar mass= grams/ moles

the grams are already given 65.18 grams. we have to find the moles to get the molar mass using the ideal gas law formula

ideal gas law---> PV= nRT

P=2.25 atm
V= 4.81 Liters
R= 0.0821 atm·L/ mol·K
T= 350 K
n= moles ???

we can rearrange the formula to solve for moles. 

n= PV/RT

n= (2.25 x 4.81) / (0.0821 x 350 K)= 0.377 moles

molar mass= 65.18 grams/ 0.377 moles= 173 g/mol